Shingled magnetic recording (SMR) is a recording system that offers higher areal density than other conventional designs. As shown in FIG. 5, in conventional SMR systems, a main pole (only the tip or corner 506 of which is shown) of a magnetic head is used to write tracks in a shingled arrangement, progressively overlaying a portion of a previously recorded track when a new track is recorded, hence the descriptive name, such that recording is performed with overlapping tracks. Consequently, the actual tracks are recorded using the main pole tip 506, so the recording characteristics of the main pole tip 506 are somewhat determinative of overall system performance. That is to say, it is of great utility to improve the field gradient in the cross-track direction and furthermore to improve the field gradient in the down-track direction, particularly at a position of the magnetic head corresponding to the track edge, e.g., the main pole tip 506.
Some attempts at improving track edge recording characteristics has focused on increasing the field gradient by reducing the side gap width between the main pole 606 and layers around the main pole 606 which may influence the performance of the magnetic head, such as shields, biasing layers, etc. A representation of reducing the side gap width is shown in FIGS. 6A-6B, with a conventional side gap width W1 shown in FIG. 6A, and a reduced side gap width W2 shown in FIG. 6B. However, the side shield problematically absorbs the magnetic field when the side gap is simply narrowed, and the resulting field intensity is inadequate for accurate and precise magnetic recording. Critically, this precludes the ability to achieve the necessary field gradient and frustrates improvements to the magnetic recording device that may be achieved by reducing the side gap width.
With narrow-track hard disk drives in particular, it is desirable to increase the cross-track magnetic field gradient and the down-track magnetic field gradient, particularly at the track edge, while minimizing any deterioration of field intensity at the track edge in order to achieve a high signal-to-noise ratio.